The present invention relates to an exposure apparatus and method utilized in the manufacture of various types of devices, e.g., a semiconductor chip such as an IC or LSI, a display element such as a liquid crystal panel, a detection element such as a magnetic head, and an image sensing element such as a CCD.
In recent years, as the packing density and operation speed of semiconductor integrated circuits increase, the pattern line width of the integrated circuits is decreased, and a higher-performance semiconductor manufacturing method is sought for. Accordingly, as an exposure apparatus used for resist pattern formation in the lithography process of the semiconductor fabrication process, a stepper utilizing extreme ultraviolet rays such as a KrF laser (248 nm), an ArF laser (193 nm), or an F2 laser (157 nm), or a short-wavelength light beam such as X-rays (0.2 to 1.5 nm) has been developed.
In exposure using X-rays, among these light beams, a proximity exposure method of moving an X-ray mask having a desired pattern to be close to a resist-coated wafer, and irradiating the wafer with X-rays through the X-ray mask, thereby transferring the projected image of the mask pattern onto the wafer, has been developed.
In order to obtain high-intensity X-rays, an exposing method using synchrotron radiation is proposed. It is reported that, according to this method, a pattern of 100 nm or less can be transferred. A synchrotron radiation source requires large-scale facilities. A profit cannot be expected unless fabrication is performed by connecting ten or more exposure apparatuses to one light source. Hence, this method is suitable for application to a highly demanded device such as a semiconductor memory. In recent years, a device using GaAs has been put into practical use as a communication device, and a large decrease in line width is required. Communication devices are produced in an amount less than that of semiconductor memories, and many types of communication devices are produced in small amounts. When an X-ray exposure system using synchrotron radiation as the light source is introduced to the fabrication of communication devices, it will probably make no profit. For this reason, an exposure apparatus using a compact X-ray source which generates high-intensity X-rays is used in actual communication device production. The light source is called a laser plasma produced source, and ranges from one which generates a plasma by irradiating a target with a laser beam and uses X-ray beams generated from the plasma, to one which generates X-rays by generating a pinch plasma in a gas. These light sources are called point sources. According to a general exposure apparatus, one exposure apparatus main body which transfers a pattern by aligning a mask and wafer is connected to one point source.
FIG. 3 shows the schematic arrangement of a conventional point source X-ray stepper. Reference numeral 101 denotes an X-ray source unit for generating X-rays. The interior of the X-ray source unit 101 is maintained in a vacuum state. The X-ray source unit 101 irradiates a target 111 with a laser beam (not shown) to generate a plasma, thus generating X-rays 117. The X-rays 117 globally diverge from a light source 112. Part of the X-rays 117 is guided into a reduced-pressure He chamber 141 through an X-ray extracting window 113. A collimator 121 is set in the reduced-pressure He chamber 141. The collimator 121 sets the incident divergent X-rays to be parallel, and outputs them at an exposure field (reference numeral 118). The X-rays 117 generated by the light source 112 are divergent light beams. At an exposure position away from the light source 112, the intensity of the X-rays 117 decreases in inverse proportion to the distance. Hence, to obtain X-rays as much as possible to increase the intensity of the X-rays for exposure is one of the roles of the collimator 121.
A mask 131 has a transfer pattern on its membrane (not shown). A wafer 132 coated with a photosensitive agent is positioned at a position with a small gap of about 10 xcexcm from the membrane by an alignment unit (not shown). The wafer 132 is irradiated with the X-rays 118 emerging from the collimator 121, so the pattern is transferred to the wafer 132. The wafer 132 is sequentially stepped by a wafer stage 134 and is exposed successively.
The exposure apparatus is mainly comprised of the light source unit 101 and a main body 102. The X-ray source unit 101 is set on a light source unit frame 115 and is installed on the floor independently of the main body 102. This prevents heat generated by the light source 112 from being transmitted through the frame to thermally distort the main body 102, leading to a decrease in alignment precision of the mask 131 and wafer 132. This also facilitates installation of the apparatus by supporting the X-ray source unit 101 and main body 102 by different structures.
The target 111 is arranged in the X-ray source unit 101, and is irradiated with a laser beam (not shown) to generate a plasma, thereby generating the X-rays 117. The interior of the X-ray source unit 101 is a vacuum and is isolated from the reduced pressure He atmosphere of the main body 102 by the Be-made X-ray extracting window 113 with a thickness of several xcexcm. Thus, the vacuum atmosphere in the X-ray source unit 101 will not be spoiled. Beryllium has a high X-ray transmittance but does not transmit He, so Be is used to form the X-ray extracting window 113. A bellows A (reference numeral 116) is set between the X-ray source unit 101 and reduced-pressure He chamber 141 to isolate them from the outside.
The main body 102 is set in the reduced-pressure He chamber 141, and is entirely maintained with the reduced-pressure He atmosphere by an He atmosphere creating unit (not shown). This is because attenuation of the X-rays can be suppressed by setting the atmosphere where the X-rays as the exposure light pass to reduced-pressure He. The main body 102 is comprised of the collimator 121 of an illumination optical system, a mask stage (not shown) for holding and positioning the mask 131, the wafer stage 134 for holding, positioning, and stepping the wafer 132, a transfer system (not shown) for transferring the mask 131 and wafer 132, and a measurement system (not shown) for measuring the positions of the mask 131 and wafer 132. The main body 102 is installed on the floor through vibration damping units 136. A stage surface plate 135 is set on the vibration damping units 136, and the wafer stage 134 moves on it. A main body frame 137 is set on the stage surface plate 135, and the collimator 121 is fixed to the main body frame 137. When the collimator 121 is to be assembled and adjusted, it is built with its position and attitude being adjusted such that the X-rays 118 have a uniform intensity distribution on the mask surface and become incident on the mask 131 to be perpendicular to it.
The vibration damping units 136 prevent the positioning precisions of the mask 131 and wafer 132, that require precise positioning, from being decreased by vibration from the floor, so the main body 102 maintains a constant attitude. As the vibration damping units 136 are formed of pneumatic springs, it is difficult to remove low-frequency vibration (vibration of several Hertz or less) with them.
Bellows B (reference numeral 142) are set between the reduced-pressure He chamber 141 and main body 102 so the reduced-pressure He atmosphere will not be spoiled when the attitude of the main body 102 changes.
With the arrangement of the conventional case, when the position of the light source 112 undesirably shifts, its position relative to the collimator 121 of the illumination optical system changes. Then, the X-ray intensity and uniformity on the mask surface, and the exposure optical axis change undesirably. When the X-ray intensity on the mask surface is nonuniform, the resolution line width within the exposure field varies. When the optical axis changes undesirably, the pattern is transferred with a shift, degrading overlay accuracy. Either case will decrease the yield in the device fabrication.
The position of the light source 112 may relatively shift when the frame 115 of the X-ray source unit 101 deforms by a thermal change. Also, when the wafer stage 134 is stepped, the main body 102 itself swings by the driving reaction force. Since the collimator 121 serving as the illumination optical system is set on the main body 102, when the wafer stage 134 is stepped, the collimator 121 swings together with the wafer stage 134 and the like. Hence, the positional relationship between the light source 112 and the collimator 121 of the illumination optical system changes. With the attitude of the main body 102 left changed, the exposure light intensity becomes nonuniform. Thus, the next exposure must wait until the attitude of the main body 102 converges. In this respect, the throughput has room for improvement.
The present invention has been made in view of the above problems, and has as its object to provide an exposure apparatus and method with which the transfer position precision of the projection image of a mask pattern is increased, so a finer micropatterned semiconductor device can be fabricated while improving the throughput.
In order to solve the above problems and to achieve the above object, an exposure apparatus according to the present invention has an illumination optical system which generates exposure light by setting to a desired state X-rays emitted from an X-ray source that generates X-rays, and transfers a mask pattern onto a substrate. The exposure apparatus comprises a detection unit for detecting a position of the X-ray source relative to a mask, and a correction unit for correcting a position and attitude of the illumination optical system on the basis of a detection result obtained by the detection unit such that an exposure intensity becomes uniform within a predetermined allowable range. The exposure apparatus also corrects the positions of the mask and wafer relative to each other so as to correct a change in exposure optical axis.
An exposing method according to the present invention uses an illumination optical system which generates exposure light by setting to a desired state X-rays emitted from an X-ray source that generates X-rays, and transfers a projection image of a mask pattern onto a substrate. The exposure method comprises the steps of detecting a position of the X-ray source relative to a mask, and correcting a position and attitude of the illumination optical system on the basis of a detection result such that an exposure intensity becomes uniform. Also, the positions of the mask and wafer relative to each other are corrected so as to correct a change in exposure optical axis.
Preferably, this correction is performed such that an exposure intensity becomes uniform within a predetermined allowable range.
Preferably, positions of the mask and substrate relative to each other are corrected on the basis of the detection result.
Preferably, this exposure is proximity X-ray exposure.
The present invention has an illumination optical system which generates exposure light by setting to a desired state X-rays emitted from an X-ray source that generates X-rays. When transferring the projection image of a mask pattern onto a substrate with the exposure light, the position of the X-ray source relative to a mask is detected, and the position and attitude of the illumination optical system are corrected on the basis of a detection result. Thus, the precision of the transfer position of the projection image of the mask pattern is improved. A finer micropatterned semiconductor device can be fabricated while increasing the throughput.
The present invention can also be applied to a semiconductor device fabricating method comprising the steps of setting a group of fabrication apparatuses for performing respective types of processes, including any one of the above exposure apparatuses, at a semiconductor fabrication factory, and fabricating a semiconductor device in accordance with a plurality of processes by using the group of fabrication apparatuses. The method preferably further comprises the steps of connecting the group of fabrication apparatuses to each other through a local area network, and data-communicating information on at least one of the group of fabrication apparatuses between the local area network and an external network outside the semiconductor fabrication factory. Preferably, maintenance information on the fabrication apparatuses is obtained through data communication by accessing a database provided by a vendor or user of the exposure apparatus through the external network, or production management is performed by data communication with another semiconductor fabrication factory through the external network.
The present invention can also be applied to a semiconductor fabrication factory comprising a group of fabrication apparatuses for performing respective types of processes, including any one of the above exposure apparatuses, a local area network for connecting the group of fabrication apparatuses, and a gateway for enabling access to an external network outside the factory from the local area network, wherein data communication of information on at least one of the group of fabrication apparatuses is enabled.
The present invention also provides a maintenance method for any one of the above exposure apparatuses, which is set on a semiconductor fabrication factory. The maintenance method may be characterized by comprising the steps of providing, by a vendor or user of the exposure apparatus, a maintenance database connected to an external network outside the semiconductor fabrication factory, allowing access to the maintenance database from inside the semiconductor fabrication factory through the external network, and transmitting maintenance information accumulated in the maintenance database to the semiconductor fabrication factory through the external network.
According to the present invention, any one of the above exposure apparatuses may be characterized in that the exposure apparatus further comprises a display, a network interface, and a computer for performing network software, and data communication of maintenance information on the exposure apparatus through a computer network is enabled. Preferably, the network software provides a user interface for accessing a maintenance database, connected to an external network outside a factory where the exposure apparatus is set and provided by a vendor or user of the exposure apparatus, on the display, so information can be obtained from the database through the external network.
Other objects and advantages, besides those discussed above, shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part thereof, and which illustrate an example of the invention. Such an example, however, is not exhaustive of the various embodiments of the invention, and, therefore, reference is made to the claims which follow the description for determining the scope of the invention.